There are high expectations regarding utilization of pattern transfer techniques that employ a nanoimprinting method to transfer patterns onto resist coated on objects to be processed, in applications to produce magnetic recording media such as DTM (Discrete Track Media) and BPM (Bit Patterned Media) and semiconductor devices.
The nanoimprinting method is a development of the well known embossing technique employed to produce optical discs. In the nanoimprinting method, a metal original (commonly referred to as a mold, a stamper, or a template), on which a pattern of protrusions and recesses is formed, is pressed against resist coated on an object to be processed. Pressing of the original onto the resist causes the resist to mechanically deform or to flow, to precisely transfer the fine pattern. If a mold is produced once, nano level fine structures can be repeatedly molded in a simple manner. Therefore, the nanoimprinting method is an economical transfer technique that produces very little harmful waste and discharge. Therefore, there are high expectations with regard to application of the nanoimprinting method in various fields.
In the conventional nanoimprinting method, an object to be processed was uniformly coated with resist by the spin coat method or the like, to form a resist film thereon. Thereafter, the surface of the mold having the pattern of protrusions and recesses thereon is pressed against the resist film, to perform pattern transfer. However, when pattern transfer is performed in this manner, there are cases in which fluctuations occur in the thickness of residual film (residual resist film which is not pressed during imprint molding, and remains at positions corresponding to the protrusions of the pattern of protrusions and recesses of the mold; also referred to as “residue”) of the resist film on which the pattern has been transferred. There are cases in which such fluctuations in the thickness of the resist film and residual gas cause imprinting defects (missing portions of the resist film which are caused by resist material not being supplied when the mold is pressed against the resist film).
In view of the above, PCT Japanese Publication No. 2008-502157, U.S. Patent Application Publication Nos. 20090014917, 20090115110, 20070228593, and 20090148619, and Japanese Unexamined Patent Publication No. 2007-313439 disclose methods that employ the ink jet method to control the amount of resist to be coated at each region of objects to be processed, according to the pattern density (the percentage of protrusions or recesses per unit area when a pattern of protrusions and recesses is viewed from above) of patterns of protrusions and recesses when molds are pressed against the objects to be processed.
Specifically, PCT Japanese Publication No. 2008-502157 and US Patent Application Publication Nos. 20090014917 and 20090115110 disclose methods for determining intervals among a plurality of droplets when producing droplet arrangement patterns (positional distributions on objects to be processed when arranging droplets of resist material using the ink jet method) using the vertical and horizontal lengths of regions on which the resist material is coated. U.S. Patent Application Publication Nos. 20070228593 and 20090148619 disclose methods for uniformizing residual films, by designing sizes per each droplet, designing droplet arrangement patterns, designing the states of interfaces between the surfaces of the droplets and the surfaces of substrates onto which the droplets are coated, etc. Japanese Unexamined Patent Publication No. 2007-313439 discloses a method for uniformizing the intervals among a plurality of droplets on a substrate, by varying jetting intervals at the inner peripheral side and the outer peripheral side of the substrate when coating the substrate with droplets by the ink jet while rotating the substrate.
That is, the publications listed above employ the ink jet method to reduce fluctuations in the thickness of residual films and imprinting defects, by optimizing the positional distribution (droplet arrangement pattern) at which droplets of resist material are arranged on objects to be processed according to pattern densities.
However, if a droplet arrangement pattern is simply optimized according to the pattern density of a pattern of protrusions and recesses of a mold as disclosed in the publications listed above, there is a problem that imprinting defects due to fluctuations in the thickness of a residual film and residual gas cannot be suppressed in the case that droplet arrangement defects, in which droplets are not arranged according to the droplet arrangement pattern, occur. Droplet arrangement defects are likely to occur due to factors such as variations in the arrangement intervals among a plurality of droplets caused by scanning of an ink jet head in a sub scanning direction, and the droplets not being jetted caused by clogs in ink jet nozzles.
FIGS. 8A through 8C are diagrams that illustrate how droplet arrangement defects occurs due to droplets not being jetted caused by clogs in ink jet nozzles. For example, if a clogged portion 20 is present in the nozzles of an ink jet head 10 (FIG. 8A), droplet arrangement defects 21, at which droplets D are not coated on a substrate 3 according to a droplet arrangement pattern P5, occur (FIG. 8B). If a mold having a straight linear pattern of protrusions and recesses P2 is pressed against the coated droplets D in a state that the droplet arrangement defects 21 are present, sufficient resist material is not supplied at the region of the substrate 3 where the droplet arrangement defects 21 are present. Accordingly, imprinting defects 22 occur in the resist film, on to which the pattern is transferred (FIG. 8C).
The present invention has been developed in view of the foregoing circumstances. It is an object of the present invention to provide a nanoimprinting method that employs the ink jet method to coat a substrate with droplets of resist material, in which imprinting defects due to fluctuations in the thickness of residual film and residual gas are suppressed even in cases that droplet arrangement defects occur.
Further, it is another object of the present invention to provide a method for producing substrates that enables highly accurate and high yield production of substrates, in which imprinting defects due to fluctuations in the thickness of a residual film and residual gas are suppressed.